In a navigation system, it is useful to be able to update the digital map of a client device remotely using a digital map update server. For example, the client device might be a portable navigation device (PND) or other navigation device associated with a user, or could be a client server. One known technique for updating such a map involves the client device periodically downloading a complete new version of a digital map from the update server to replace a previous version of the map held by the client device. The new version of the digital map will incorporate any updates, e.g. corrections or enhancements, since the previous version of the digital map held by the client device. For example, traditionally a navigation map provider would release a new version of a digital map, e.g. quarterly, incorporating any updates since the previous version of the map, which could be downloaded by client devices.
However, more recently it has been recognised that, rather than periodically replacing the entire digital map of a client device in order to update the map, it is desirable to instead be able to only update those parts of the digital map which have changed. These arrangements are advantageous in that only updates, i.e. changes to the digital map, since it was previously updated for example, need be transmitted to the client device. The updates can be received by the client device and used to update the existing map of the device. Systems in which only updates, i.e. changes to the digital map, are provided to the client device, and used to update an existing digital map of the device, may be referred to as “incremental update” systems. Such incremental update systems provide greater flexibility, and enable the digital map of the client device to be kept more regularly updated, rather than being limited to periodic updating when a new version of the map is released. For example, the digital map may be updated once a week, or once a day, or at any desired interval. Furthermore, incremental update systems are less demanding in terms of processing power and/or memory of the client devices, enabling updates to be implemented more easily, e.g. on the fly. There are, however, certain challenges in implementing incremental update systems for updating the digital map of a remote client device.
Certain particular difficulties revolve around ensuring consistency and quality of the digital maps of client devices in an incremental update system.
The Applicant has realised that there remains scope for improvement in systems and methods for providing incremental update data for use in updating an existing digital map of a remote client device.